Temporal Dynamics of Implicit Attentional Guidance by Binary Categorization of Numerical Stimuli in Visual Search

The binary categorization of numerical sequential information can produce a category effect in visual search, with faster and more accurate performance in between-category than within-category. However, it remains unclear how the binary categorization guides attention during the searching process. To clarify this, we conducted one behavioral experiment and one eye-tracking experiment to explore the category effect in a dynamic temporal view. Experiment 1 used eight numbers as stimuli (1,2,3,4,6,7,8,9), and two conditions of within-category and between-category were divided according to midpoint-precedent (1,2,3,4) and midpoint-antecedent (6,7,8,9) numbers. Results showed a stable category effect that participants' reaction times were faster in the between-category condition. Further temporal dynamics analysis showed this category effect increased as the reaction time prolonged, which indicates that the category information exerts a gradually amplifying, late-stage influence on attentional selection rather than an early fixed perceptual effect. Experiment 2 adopted the eye-tracking technology to further analyze the temporal distribution of fixation proportions on target versus distractor arrays. Results showed a fixation dominance on target versus distractor arrays earlier in the between-category condition (401–500 ms) than that in the within-category condition (501–600 ms). During the subsequent time course, target fixation proportion was greater than distractor in the between-category condition, while the within-category condition showed a comparable pattern with a smaller, non-significant difference. Collectively, these findings confirm that binary categorization of numerical sequential information exerts a temporally specific regulatory effect on visual search by modulating early attentional orienting efficiency and late maintenance stability, thus determining overall search performance.